Doctoring device for balling-up drum



April 22, 1958 F. D. DE VANEY 2,831,210

DOCTORING DEVICE FOR BALLING-UP DRUM Filed Feb. 16, 1951 4 Sheets-Sheet1 E INVENFOR GEM/J 2 WW A omen Ff h INVENTOR I J/ t AJWLDD am a L w FMApril 22, 1958 F. D. DE VANEY 2,831,210

DOCTORING DEVICE FOR BALLING-UP DRUM Filed Feb. 16, 1951 4 Sheets-Sheet2 THY" ATTORNEYS April 22, 1958 F. D. D VANEY 2,831,210

DO CTORING DEVICE FOR BALLING-UP DRUM U A w" 4 I I INVENTOR L5 BYATTORNEYS (I ll A ril 22, 1958 F. D. DE VANEY 2,331,210

DOCTORING DEVICE FOR BALLING-UP DRUM Filed Feb. 16, 1951 4 SheetsSheet 4INVENTOR d'ikz. 0424 I /PM ATTORNEYS ited taes i DUCTORLWG DEVECE FGREALLlNG-UP DRUM Application February 16, 1951, Serial No. 211,290

11 Claims. (Cl. 18-1) This invention relates to the art of agglomeratingfinely divided mineral material, especially ore concentrates and fines,and is concerned with improvements in that form of agglomeration whereininitially homogeneously moist finely divided mineral material ispelletized'or balled up by passage through a rotatingdrum and thepellets thereupon are'indurated (heat hardened) under conditions toprovide mechanically rugged, rock-like bodies.

It has now been found that desirably rugged balls which have amaterially reduced tendency to exfoliate canbe produced inanindustrially feasible manner, by the following improved procedure: Theballing-up or -forming-operatiun is carried out in a special form ofrotary drum, wherein are observed those conditions (to be moreparticularly described hereinbelow) as regards character of surface overwhich the pellets are rlled,-rnode of insuring proper rolling of thecharge, depth of bed, length of path, peripheral speed of the drum, andother factors which have been found best adapted to the formation ofrugged balls of the desired $126.

It has been found advantageous to conduct the forming operation in aclosed circuit, i. e., to pass the feedconsisting of fresh moist finesand returned undersized balls or particles from a previous pass-21plurality of times through the forming drum under conditions to prornotea relatively slow growth of balls to their desired full size. Thus, ithas been found advantageous so to operate the process that in any onepass through the drum the feed consists of about one-third fresh moistfines and about two-thirds of seed balls from a previous pass. it hasbeen found advantageous, also, to provide a long path of rolling (eitherby inclining the drum only slightly or by extending the length of thedrum, or both), and so to feed that the volume of material being actedon is small with relation to the volume of the drum (whereby to maintainonly a relatively shallow pool of the feed material in the drum), and torotate the drum as rapidly as possible short'of that speed at which thefeed material tends to be thrown through the air. And, it has been foundadvantageous if not necessary to form the balls-and to cause seed ballsto grow by slow accretionby rolling the feed material on a rollingsurface consisting of a relatively dense, i. e., compacted, layer of themoistfines lining the inner periphery of the balling-up drum, theexposed surface of which layer is characterized by a controlledroughness. This lining should be relatively thin as it is not restrainedagainst accidental dislodgment en gross from the drum surface.

Of particular importance to the success of a balling-up process of thetype herein contemplated is the maintenance on the inner surface of thedrum of a'rolling surface of controlled thickness and roughness. Thus,it has been found that when the surfacesupporting the feed material issmooth, as obtains when the feed material lies adjacent a smooth rubberlining of the drum, ,or as obtains when a compacted layer of the moistfines is continuously maintained smooth by use of a doctor blade assuggested in Firth Patent No. 2,411,873, the seed balls-and feedmaterial in tote-tend to slide, rather than to, roll, on the slicksurfacethus provided, thereby depreciating the desired result. Moreover,when a broad doctor blade is utilized to work against the cak of moistfines, the cake becomes harder and harder thus making it increasinglydifiicult to scrape/ Also there is a tendency for the drum to chatterand the power consumption is greatly increased.

I have found that the above referred to conditions of controlledthickness and roughness of the surface 'supporting the feed material canbe achieved by continuously doctoring the rolling surface at a pluralityof small axially separate areas at a time, said areas beingprogressively axially shifted so as to effect eventual substantiallycomplete coverage of the rolling surface.

Operable means for effecting the doctoring of the rolling surface asabove described are diverse. Thus, the doctoring tools may be teethwhich present spaced points to the rolling'surfacesimilar to the teethof a comb, but preferably they are teeth which present to the rollingsurface a plurality of spaced chisel-like edges each a fraction of aninch wide a it is desirable that the toothed cutter bar be locatedon'the upcoming side of the drum, so that the cuttings fall onto therolling balls and be readily reformed. If the cutter bar were so placed,e. gl, on the downcoming side, that the cuttings fell onto the shell,the cuttings would be carried under the balls where they would causeirregularities; moreover, cuttings so rolled on do not readily reforminto balls. The teeth are mounted several inches apart along a rigid,non-rotating doctor or cutter bar extending through the rotary drum. Thecutter bar is associated with means for reciprocating the same parallelto said rolling surface, whereby progressively to shift the teethlongitudinally so as to induce the doctoring, by each of the latter, ofa series of allochiral, i. e. righthand and left-hand helical"groovesthe adjacent turns of which are spaced apart. Care is taken so to adjustthe rate of reciprocation of the cutter-bar and the rate of rotation ofthe rotary drum that the .grooves cut by any one tooth do not track witheach other on successive strokes of the cutter bar, to the end that theteeth edges in the course of a reasonable time interval shall havecontacted substantially all of the area of the rolling surface.

A preferred constructional embodiment of the invention is shown in theaccompanying drawings in which:

Fig. l is a View in side elevation of the balling drum, the improveddoctoring apparatus and essential auxiliary components;

Fig. 2 is a top plan to better illustrate the doctoring apparatus;

Fig. 3 is a view in vertical transverse section through the drum;

Fig. 4' is a side elevation with some parts in section of the supportfor one end of the doctor bar and the reciprocating drive therefor, theview being drawn to an enlarged scale; s

Fig. 5 is a vertical transverse section on line 5- 5 of Fig. 4; v

Fig; 6 is an enlarged fragmentary view illustrating constructionaldetailof the trommel at the discharge end of the balling drum forscreening out undersized balls;

Fig. 7 is a transverse section taken on line 77 of s- Fig. 8 is an endview of the trommel at the discharge side thereof;

Fig. 9 is an enlarged, fragmentary detail of the interior of the ballingdrum; and I V view with certain parts broken away 9 Fig. 10 is atransverse section on line 10-10 of Fig.

With reference now to'Figs. 1-3 in particular, the balling up apparatus:is seen to be comprised of an open ended cylindrical steel drum 10about 18 feet long and t; feet in diameter. The drum is supported forrotation in two cradles 12, 13 having smooth rollers 14, 15,respectively, which engage peripheral steel tires 16, 17 on the drum 10.Cradles 12, 13 are carried by a framework of steel beams 18 in order toraise the drum sulficiently above the floor line to accommodate the associated conveyor system, driving motors and other related components.Drum 10 is maintained in place on rollers 14, by means of athrustbearing, constituted by roller 8 journalled on the spindled upper end ofupstanding post member 9 supported on frame 18, which thrust bearingbears against a steel ring 19 encircling and secured to drum 10. Inorder to effect movement of the material being balled up axially throughthe drum 10 as the latter rotates it will be observed that the forwardcradle 12 adjacent the loading end 10a of the drum is situated at alevel higher than the rear cradle 13 adjacent the discharge end, thusdeclining the drum in the direction of its discharge end 10b. Thedeclination is preferably of the order of A inch to 1 inch per foot oflength but has been somewhat exaggerated in the drawing to more clearlyindicate its sloping characteristic.

For rotating drum 10* continuously in one direction only there isprovided a sprocket and chain type of drive comprising a driven sprocket20 surrounding the drum, a driving sprocket 21 secured to the shaft of amotor 22 preferably of the type in which its speed can be varied, and achain 23 extending between the two sprockets. The optimum speed for adrum of the dimensions indicated has been found to be 10.8 R. P. M.,which gives a peripheral speed of approximately 275 ft./min. Aspreviously explained, the drum speed is not too critical but is,however, important since the upper speed limit must be somewhat belowthat at which the balls tend to be thrown from, rather than roll along,the interior surface of the drum.

For screening out undersized balls, a circular trommel 25 is disposed atthe discharge end 1011 of the balling drum. The trommel is preferbaly ofthe form shown in the drawings, consisting of generaly frustoconicalskeleton framework made up from an array of lengths of angle stock 26held in spaced relation by a plurality of axially spaced bands 27 and ahelix of round bar stock 28 secured to plates 29 upstanding upon theangles 26 as best shown in Figs. 6 and 7. The diameter of the bar stock28 and the spacing between adjacent turns thereof will be dictated bythe size of ball desired to be returned for another pass through theballing drum 10 for further growth. In the embodiment of the inventionas actually constructed, however, the bar stock used for forming thehelical screen was 1 in diameter and the distance between centers ofadjacent turns of the helix was giving a clear opening of 5.

The wires or rods which make up the screening surface of the trommel maybe either concentric or-as shownspirally disposed in a direction whichwill tend to facilitate discharging the finished balls.

The internal diameter of trommel 25 at its inlet end 25a is slightlylarger than. the externaldiameter ofdrum 10 so as to permit the formerto telescope over the-latter, and its discharge end 25b has an internaldiameter larger than that at the inlet end 250 thus establishing atapered surface dipping in the direction of the feed of the ballsthrough drum 10. The trommel is disposed with its major axis horizontal.In the actual construction, the internal trommel diameters at the inletand outlet ends were approximately 8.5 feet and 9.2 feet, re-

spectively. .The declination; of the inside surface of As in the case ofdrum 10, the trommel 25 is sup ported on two cradles 31, 32 providedwith sets of grooved rollers 33, 34, respectively, which engage steeltires 35, 36. Trommel 25 also rotates and its driving mechanism is alsoof the chain-sprocket type including a driven sprocket pinion 37 keyedto shaft 38 (see Fig. 1) to which shaft roller 34 is also keyed, adriving sprocket 39 on the drive shaft of motor 40 and a chain 41.Preferably trommel 25 rotates at approximately 7 R. P. M., i. e.,slightly slower than drum 10.

It is to be noted that in a case where the diameters of the drum andtrommel differ from the specific values above mentioned the drum andtrommel are to be operated at speeds which will give approximately thesame relation of peripheral speeds, in feet per minute.

At the discharge end 2511 of the trommel as seen in Fig. 8, a transversebarrier 42, supported by suitable bracket means 42a, is erected todeflect balls, which may have been caught in the trommel opening, andcarried to near-the top of the trommel, in such manner that such ballsmay drop onto the screening surface rather than fall into the discharge.As shown in Fig. 1, balls, discharge from trommel 25 onto conveyor belt81, to be carried by the latter to a point of use or further treatment.Advantageously, conveyor belt 81 is disposed withits long axis normal tothe horizontal axis of trommel 25.

Reverting to the drum 10, and with particular reference to Figs. 2, 9and 10, it will be seen that the interior surface ofv the steel drum 10is lined with a layer of concrete .47 preferably from 1 to 3 inchesthick or other material having a moderately rough surface such as anexpanded metal lathe, upon which is allowed to build a second denselayer 48 of the moist ore fines. Layer 48 is maintained at a thicknessof approximately 1 inch by the doctoring device and is the layer uponwhich the seed balls are caused to roll and grow slowly in diameter bythe process of accretion.

As explained in the introduction, it is most important that the seedballs be made to roll rather than slide upon the interior. surface ofthe drum 10. To this end, the present invention provides for maintainingan optimum degree of roughness on the surface of layer 48 andspecificallyrby means which continuously doctor the surface at aplurality of small and axially separate areas at a time, the doctoredareas being progressively axially shifted ,so asto eifect eventualsubstantially complete coverage of the rolling surface.

Apparatuswise, doctoring of the surface layer 48 is done by means of adoctor or cutter bar extending longitudinally through the drum 10 andtrommel 25 as shown at 51). Bar 50vis positioned at the 2 oclockposition, so that cuttings produced by its teeth, duringcounterclockwise rotation of the drum, as viewed in Fig. 3, may falluponthe rolling balls. Bar 50 is preferably made from 10" diameter,extra heavy pipe in order to insure axial rigidity, and has secured toit a plurality of teeth 51 projecting laterally therefrom and positionedto engage and cut the surface of layer 48. The cutting edge of eachtooth is preferably constituted by a renewable insert 52 made from ametal carbide such as that sold under the tradename .Carset, andpresents a cutting edge about 0.25" in width. At the inlet end to drum10, the teeth 51 are spaced comparatively close together, i. e., about 4apart for an axial distance of about four feet in order to cope with theheavy build-up of feed material which tends to deposit at a greater rateat this end of the drum. The spacing between the teeth 51 for theremainder of the'axial lengthof the drum is approximately 8".

Provision is made to reciprocate the cutter bar 50 at a rate of fourstrokes per minute and the length of the stroke of reciprocation isabout 8.25" (i. e., just enough to insure the meeting of areasinfluenced by adjacent ones of the 8" spaced teeth). The reciprocatingmotion of the cutter bar 50 coupled with rotary motion of drum resultsin a doctor pattern consisting of a series of 0.25 wide criss-crossallochiral' spiral grooves. The grooves of one hand cut bysuccessivepasses of the cutter teeth in one direction are designated by numeral 49and those of the opposite hand produced by successive passes of thecutter teeth in the opposite direction are designated by numeral 49'.With the dimensions and rate of motion given, the grooves cut in thelayer 48 by any one of the teeth 51 during successive strokes of thecutter bar will not track or register with each other thus assuringworking of the entire surface area of the compacted layer 48 of moistfines in due course. While the base of each groove so cut presents asmooth surface that would tend to cause a sliding movement of the ballsthe groove is narrow enough to prevent the smallest of the seed ballsfrom getting down into it. Thus the surface of layer 48 is maintained ina constant state of roughness and never presents any smooth portionswhich could cause the balls to slide.

Each of the criss-crossed right and left hand grooves 49, 49' andparticularly those near the loading end of drum 10 actually begin torefill with the moist fines present in the drum not long after they havebeen cut by the teeth 51. Consequently the grooved doctor pattern wouldactually not acquire a degree of distinctiveness as sharp asthatpictured in Fig. 9 which has purposely been exaggerated in order tomore clearly illustrate this important aspect of the present invention.

The roughened surface of layer 48 causes the balls to be carried up thewall of the drum 10 as the latter rotates until the holding friction isovercome whereupon the balls then roll down the drum wall and accumulatemor of the loose moist fines.

The cutter bar 50 is supported at each end thereof by a wheeled axlethat rolls on an associated trackway.

The enlarged views of Figs. 4 and 5 show the details of constructionemployed at the end connected to the motor which furnishes the power forreciprocating the cutter bar. Here the details are seen to include anopen-ended rectangular housing 54 the side walls of which are providedwith confronting K-shaped channels 55 which serve as a trackway for thewheels 57 journalled on axle 58. A cap 59 is fitted upon the end of bar543 and brackets 60 connect the cap 59 and hence the cutter bar to axle58.

A crank arm 61 having one end thereof pivotally secured by a clevis 62to axle 58 extends to an eccentric plate 63 which is secured upon theoutput shaft 64 from a speed reduction unit 65 powered by motor 66.Plate 63 is preferably provided with a plurality of eccentric pins 63alocated at ditferent radii from the center, to any one of which crankarm 61 is connected thereby enabling one to adjust the stroke of thecutter bar 50.

The support for the opposite end of the cutter bar is similar includingan open-ended rectangular housing 67 having [-shaped channels 68 forminga trackway for wheels 69 journalled upon axle 70 to which the capped endof the cutter bar is secured. As shown in Fig. l the trackway channels55, 68 preferably are inclined at the same angle as the balling drum 10.

To the underside of the trackway housings 54, 67 and also the supportplate 71 for motor 66 are secured channel members 72 which seat upon eyebeams 73. Cutter bar 50 is preferably so disposed that the teeth 51 cutto within about one inch from the inner surface of the concrete liner47i. e., the compacted layer 48 of moist fines left undisturbed by theaction of the teeth is about one inch thick.

To compensate for tooth wear and other variable factors, provision ismade for adjusting the cutter bar 50 transversely of its axis. To thisend and with reference to Fig. 5 in particular it will be seen that thechannels 72 and hence housings 54, 67 are slidable longitudinally alongbeams 73 and are fixed in any selected position of adjustment by meansof spaced pairs of adjusting screws 74 the ends of which bear againstthe outer surface of the housings 54, 67. The screws 74 thread throughbrackets 75 secured upon beams 73 and hence the housing adjust ment maybe effected by turning down the screws 74 at one side of the housingsand backing off by a corresponding amount the screws at the other sideof the housings. Motor 66 must also be adjustable transversely tomaintain alignment in the connections between the motor and cutter bar,and hence it will be seen that similar adjusting screws 76 are providedfor engagement with the upturned sides 71a of the motor support plate'71.

It will be remembered from the introduction that the balling up processcontemplates passage of the initially small seed balls on an average ofthree times through the balling drum 10in order to promote a slow growthof the balls to the desired minimum diameter. The same efiect is notsecured by tripling the length of the balling drum; for the desiredgrowth, partially grown balls should be returned to the drum and come incontact with fresh new feed.

A conveyor system is employed, and is best shown in Figs. 1, 2 and 3. Aninclined endless belt type of conveyor 77 located beneath and extendingtransversely of the trommel 25 receives all undersized balls and finesthat drop through the interstices in the helical screen 28. Conveyor 77carries the balls and fines laterally outward from the trommel anddischarges onto another inclined endless belt conveyor 78 extendingparallel with the drum 10, and which is used to transport the materialrearwardly to the loading end of the drum. Here the material istransferred to another belt conveyor 79 for transport laterallyinwardand final discharge upon conveyor 86 on which the fresh fines andseed balls are brought to the loading end of drum 10 which is coned asshown to prevent spillage. After the balled up ore fines have grown to adiameter where they no longer are able to pass through the trommelscreen, they will discharge onto conveyor 81 for transport to theindurating furnace.

In conclusion, it will now be evident that the improved method andapparatus for doctoring the surface of the compacted layer of ore finesserves not only to keep the layer from building up to such thickness andweight where large portions would tend to break off but also maintainsthe surface of the layer in a state of roughness which enhances thedesired rolling action of the balls along the interior of the drum andreduces any tendency on the part of the balls to slide rather than roll.

Moreover, it is to be understood that while the embodiment of myinvention as illustrated is to be preferred, various minor changes maybe made in the construction and arrangement of the component partswithout, however, departing from the spirit and scope of the inventionas defined in the appended claims.

I claim:

1. Apparatus for forming moist finely divided loose mineral matter suchas ore fines into balls comprising an inclined elongated hollow drumhaving, during use, at least the greater part of its inner surface linedwith a compacted layer of the ore fines constituting a rolling surfacefor the loose fines, means for feeding loose fines into the higher endof said drum, means for rotating said drum on its longitudinal axis,doctoring means for continuously limiting the thickness of suchcompacted layer, said doctoring means being stationary with respect tothe rotation of said drum and adapted to contact, and continuously limitthe thickness of, said compacted layer along a plurality of spacedapart, relatively narrow, parallel paths extending circumferentially ofthe exposed surface of said compacted layer, said doctoring meansincluding means for shifting the paths progressively in a directionlongitudinally of said drum so as to effect eventual doctoring of theentire area of said compacted layer.

2. Apparatus for forming moist finely'divided loose mineral matter suchas ore fines into halls comprising, an inclined elongated hollow drumhaving, during use, its inner surface lined with a compacted layer ofthe ore fines constituting a rolling surface for the loose fines, meansfor loading loose fines into the higher end of said drum, means forrotating said drum about its longitudinal axis, a plurality ofrotationally stationary relatively closely spaced and narrow teethdisposed longitudinally of said drum in engagement with said compactedlayer to mal-1e a series of generally parallel cuts in the latter, and

means for progressively shifting said teeth longitudinally of said drumsimultaneously with rotation of the latter thereby to cause each of saidteeth to make a spiral cut in the surface of said compacted layer.

3. Apparatus for forming moist finely divided loose mineral matter suchas ore fines into balls comprising, an inclined elongated hollowdrum-having, during use, its inner surface lined with a compacted layerof the ore fines constituting a rolling surface for the loose fines,means for loading loose fines into the higher end of said drum, meansfor rotating said drum about its longitudinal axis, a plurality ofrotationally stationary relatively closely spaced and narrow teethdisposed longitudinally of said drum in engagement with said compactedlayer to make a series of generally parallel cuts in the latter, and

means for reciprocating said teeth longitudinally of said drumsimultaneously with rotation of the latter thereby to cause each of saidteeth to make a series of non-registering allochiral spiral cuts in thesurface of said compacted layer.

4. Apparatus for balling-up mineral matter as defined in claim 3 whereinthe stroireof reciprocation of each tooth is substantially equal inlength to the spacing between the widest spaced teeth.

5. Apparatus for balling-up mineral matter as defined in claim 3 whereinthe teeth at the loading end of said drum are more closely spaced thanthe remainder thereof.

6. Apparatus for forming moist finely divided loose mineral matter suchas ore fines into balls comprising, an inclined elongated hollow drumhaving, during use, its inner surface lined with a compacted layer ofthe ore fines constituting a rolling surface for the loose fines, meansfor feeding loose fines into the higher end of said drum, means forrotating said drum about its longitudinal axis, a rigid cutter barextending longitudinally Within said drum, a plurality of rotationallystationary relatively closely spaced and narrowteeth arrangedlongitudinally of said bar and secured thereto, said teeth beingpositioned to engage said compacted layer to make a series of generallyparallel cuts in the latter, and means for reciprocating said cutter barlongitudinally of its axis simultaneously with rotation of said drumthereby to cause each of said teeth to cut a series of non-registeringallochiral spiral grooves in the surface of said compacted layer.

7. Apparatus for balling-up mineral matter as defined in claim 6 whereinthe stroke of reciprocation of said cutter bar is substantially equal inlength to the spacing between the widest spaced teeth.

8. Apparatus for balling-up mineral matter as defined in claim 6 andwhich further includes means for adjusting said cutter bar, in adirection normal to its. longitudinal axis thereby to ieifect anadjustment in the depth of cut of said teeth.

9. Apparatus for forming moist finely divided loose mineral matter suchas ore fines into balls comprising, an inclined elongated hollow drumhaving, during use, its inner surface 'linedwith a compacted layer of.the ore fines constituting a rolling surface for the loose fines,meansfor feeding loose fines into'the higher end of said drum, means forrotating said drum about its longitudinal axis, a rigid cutter barextending through said drum, a wheeled axle supporting said bar at eachend thereof, a trackway for each of said Wheeled axles extendinglongitudinally of said bar, a plurality of relatively closely spacedand'narrow teeth arranged longitudinally of said bar and securedthereto, said teeth being positioned to engage the surface of saidcompacted layer, and means for reciprocating said wheeled axles andhence said bar longitudinally of its axis simultaneously with rotationof said drum to cause each of said teeth to cut a series ofnon-registering allochiral 'spiralgroovesin the surface of saidcompacted layer.

10. Apparatus for balling-up mineral matter as defined in claim 9 andwhich further includes means for adjusting said trackways and hence saidbar in a direction transverse to the longitudinal axis of the latterthereby to effect an adjustment in the depth of cut of said teeth.

11. Apparatus for forming moist finely divided-loose mineral matter suchas ore fines into ballssaid apparatus comprising an inclined elongatedhollow drum having,

during use, at least the greater part of its inner surface lined with acompacted layer of the moist ore 'fines constituting a rolling surfacefor the loose fines-means" for feeding loose moist fines into the higherend of the drum, means for rotating said drum on its longitudinal axis,means operatively associated with the lowerend-of said drum forscreening loose moist fines and undersized balls from the productcontinuously discharged from the lower end of said drum, means forreturning the screenings to the higher end of said drum, and doctoringmeans for continuously limiting the thickness of such compacted layer,said doctoringmeans being stationary with respect to the rotation ofsaid drum and adapted to contact, and continuously limit the thicknessof, said compacted layer along a plurality of spaced apart, relativelyvnarrow, parallel paths extending circumferentially of the exposedsurface of said compacted layer, said doctoring means including meansfor progressively shifting the 'paths 'in the direction of thelongitudinal axis of the drum whereby to effect eventual doctoring ofthe' entirearea of said compacted layer.

.References Cited in. the, file of this patent UNITED STATES PATENTS1,540,662 Stone June 2; 1925 1,775,313 Lellep Sept. 9; 1930 1,883,112Tiers Oct; 18, 1932 1,980,130 Fasting 'Nov.6, I934 2,293,439 Lloyd Aug.18, 1942 2,357,941 Eirich-et a1 Sept. 12, 1944 2,422,989 Skoog June 24,1947

